Machining tool and method for manufacturing a machining tool

ABSTRACT

A machining tool, in particular a drill carrier tool, includes a monolithic base body extending in the axial direction which, at least in one section, has a porous or grid-like core structure that is encased in a solid outer jacket. These measures allow less material to be used, while maintaining good mechanical properties. The porous or grid-like core structure is simultaneously used for transporting coolant. The base body is manufactured in particular by means of a 3D printing method.

FIELD OF THE INVENTION

The invention relates to a machining tool, in particular a rotating toolsuch as a drill or milling tool, having a monolithic base body extendingin an axial direction. The invention additionally relates to a methodfor manufacturing a machining tool of this type.

BACKGROUND OF THE INVENTION

Machining tools, in particular drills, usually have a clamping shaftextending in the axial direction to which a slotted cutting partconnects which extends up to a front tool tip, in particular to a drillbit. In the case of such machining tools, which are also referred to asshaft tools, coolant channels are often formed in the interior of thebase body, as can be seen in EP 0 843 609 B1, for example.

In what are referred to as solid carbide drills, a monolithic base bodyis formed as a sintered body. The manufacturing process involves firstmaking a base body by compression from a metal powder as sintermaterial, for example, which is then sintered. U.S. Pat. No. 7,226,254B2 discloses a sintered base body in which, to save sinter material, acentral recess is made in the base body in the area of the clampingshaft prior to sintering said base body. The sinter material thus savedis used for manufacturing additional tools.

SUMMARY OF THE INVENTION

Based on this, the invention forms a basis for providing a machiningtool as well as a method for the manufacturing thereof, in which anefficient use of material and good mechanical properties are bothensured.

The problem is solved according to the invention by a machining toolhaving the features of claim 1. The machining tool is a rotating tool inparticular, such as a drill or milling tool, for example. It comprises amonolithic base body extending in the axial direction in which anon-solid core structure is formed, at least in a section extending inthe axial direction, which is encased by a solid outer jacket. The outerjacket annularly encases the non-solid core structure preferably at aconstant wall thickness. A large part of the base body is deliberatelydesigned to be not solid due to the core structure which is non-solidcompared to the solid outer jacket, thereby saving not only weight, butalso material. At the same time, sufficiently high mechanical stabilityis achieved by the special core structure with the solid outer jacketstructure. In this way, the core structure provides a type of mechanicalsupport structure.

In this respect, it is especially important that the base body is amonolithic body. This term is understood to mean that the base body,i.e., in particular also the combination of the core structure with theouter jacket, is constructed from a single body, i.e., is made from onepiece and is not assembled from two or more parts, e.g., by welding,soldering, bonding or similar.

The term non-solid core structure is generally understood to mean thatopen areas are formed in the core structure in which no material ispresent.

The core structure is preferably optionally porous, grid-like or evenbionic. The term porous is generally understood to mean a structure inwhich individual pores are preferably scattered, i.e. unstructured andomnidirectional in the material of the core structure. Both open-pore aswell as closed-pore structures are possible. In the case of an open-porestructure, on the whole, the core structure is permeable to a gas orliquid, such as a coolant, for example.

The term grid-like is understood to mean a structure in which areas thatare free of material are separated from one another by partitions, inparticular channels, usually in an ordered material structure, forexample a periodic material structure. These individual channelspreferably extend in the axial direction.

A bionic structure, in contrast, is understood to be an unordered, inparticular non-periodic arrangement of partitions of this type, based,in particular, on patterns from nature.

According to the invention, the machining tool is manufactured with theaid of a method having the features of claim 12, which provides that thebase body is manufactured with the aid of a 3D printing method. In themeantime, 3D printing methods have been used for a wide variety ofapplications. These methods basically involve processing a powderystarting material layer-by-layer with a laser, such that the individualpowder particles bond to one another, for example, melt with or sinterwith one another layer-by-layer into a solid, rigid body. Thelayer-by-layer, stratified construction makes it possible to easily formundercuts and complex geometrical structures, which, with previousconventional manufacturing methods, was not possible or requiredconsiderable effort and expense. In this case, a metal powder having anaverage grain size ranging between 10 and 50 μm is used as a startingmaterial in powder form. In particular, the material for the metalpowder is a tool steel.

Accordingly, this specific method, which makes it possible to createvery fine structures, is provided for forming the specific non-solidcore structure in the present invention.

The machining tool is optionally an monolithic tool taken as a wholehaving a tool tip integrated into the base body or, alternatively, it iswhat is known as a carrier tool consisting of a support made up of thebase body and a preferably reversibly replaceable cutting elementapplied thereon.

The machining tool generally has at its front end a tool tip which isitself designed as a cutting element or one or more cutting elements arearranged in the area thereof. In the present invention, a tool tip isthus generally understood to mean the frontal end area of the machiningtool, i.e. a forward face area of the machining tool. If the tool isdesigned as a modular carrier tool, a replaceable cutting element(cutting insert) is attached to the base body. According to a preferredvariant, the tool tip itself is designed as a replaceable cuttinginsert. This can be reversibly and replaceably attached to the base bodyby clamping, for example, with the aid of fastening elements such asscrews, or alternatively by simple turning. In this way, it is heldclamped in particular between two retaining or clamping strips of thebase body. Alternatively, the carrier tool is designed with plate seatsfor attaching (indexable) cutting inserts. In this case, the area of theplate seats is understood to mean the tool tip. In a non-modular,one-piece tool having, for example, major cutting edges cut into the endface area, a front end face area having an axial length in the range ofa nominal diameter, for example, constitutes the tool tip.

Drills and milling tools in general are classified as rotating tools. Itis thus understood that, during operation, the machining tool rotatesaround a center axis which at the same time defines the rotational axis.

A further advantage of the core structure centrally formed in the basebody is that it is of lower density than the solid annular outer jacket.This results in a density distribution with greater density in the outerarea, which results in a more stable rotation, particularly in rotatingtools. The core structure is preferably designed to be rotationallysymmetrical and preferably circular, at least rotationally symmetricalwith at least a two-fold to six-fold rotational geometry.

To give it an especially high mechanical rigidity, the core structure isexpediently designed as a honeycomb structure. This constitutes aspecial type of grid-like core structure in which the individualchannels have a hexagonal cross-section.

In the case of a grid-like core structure, for example a honeycombstructure, a plurality of longitudinally extending channels are formed.In the present invention, the term plurality is understood to mean inparticular that at least five, preferably at least eight or evensignificantly more channels are incorporated. The individual channelsexpediently have a maximum channel width below 0.5 mm and in particularbelow 0.10 mm.

If the core structure is porous, it expediently has a porosity rangingbetween 5 and 90%. This means that, compared to a solid body, between 5and 90% of the volume consists of pores. The pores preferably have anaverage pore size ranging between 15 and 45 μm.

The core structure expediently has, at least in a shaft part, a circularcross-section and is designed to be concentric in particular to theannular outer jacket. The core structure as well as the outer jacket arethus coaxial to the center axis and in particular to the rotationalaxis.

Overall, the core structure covers an area of preferably around 5 to 80%of a total cross-sectional area of the base body. If the core structureis circular, it has a core radius that is preferably between 50 and 90%of an outer radius of the base body. Formed thereon is a comparativelynarrower circumferential solid rim forming the outer jacket, preferablyof constant wall thickness, which, however, is sufficiently dimensionedfor the required mechanical loads, for example the clamping forcespresent when clamping the base body. The core structure portionexpediently varies in the axial direction. In particular, the portion ofthe core structure differs between a front fluted cutting part and arear shaft part. In the front cutting part, the portion of the corestructure is in the lower range, for example between 5 and 30%, while inthe shaft part it is in the upper range, for example between 40 and 80%,relative to the total cross-sectional area (recesses, such as chipflutes for example, do not count toward total cross-sectional surface).

In a useful embodiment, the core structure comprises a cross-sectionalarea that changes in the axial direction. In principle, the specialmanufacturing method of 3D printing allows any desired structure to becreated. In the present invention, this method is utilized to the extentthat a core structure geometry specifically adapted to the base bodygeometry is created in different axial sections of the base body.Varying the cross-sectional geometry additionally allows mechanicalproperties to be suitably adjusted at defined axial positions. Inparticular, allowance is made for highly loaded sections, for example,by enlarging the wall thickness of the solid outer jacket in thesesections.

In an especially expedient refinement, solid struts are introduced intothe core structure in the direction of the center axis to therebyachieve additional improvement in rigidity. Struts of this type areexpediently bent in the shape of a sickle, for example, to transmitincreased mechanical loads arising at the cutting edges into theinterior of the base body, for example. The number of struts introducedis expediently equal to the number of cutting edges distributedcircumferentially. If two circumferential cutting edges are present, thetwo struts preferably merge into one another in the center axis and are,for example, wound on the whole into the shape of an S. The struts form,for example, a structure in the shape of spokes and spoked wheel. Thestruts basically have a wall thickness significantly greater than thenormal wall thickness of the grid-like core structure. For example, theyare many times greater than the normal wall thickness. The wallthickness of the struts also preferably varies depending on their radialposition, and specifically preferably varies continuously.

The base body usually comprises a shaft part as a clamping shaft withwhich it is clamped into a clamping device of a machine tool. The centeraxis of the machining tool is oriented so that it is precisely coaxialwith the rotational axis of the machine tool. Connecting to the front ofthe shaft part in the axial direction is a front cutting part, which isusually provided with chip flutes. These are designed to either run in astraight line or to run helically. In an expedient design, the corestructure further extends into the cutting part starting from the shaftpart, so that a continuous core structure is formed. In this case, thecore structure preferably has a circular cross-sectional geometry in theshaft part, which transitions into an altered geometry in the cuttingpart.

The core structure is expediently designed to be elongated in the areaof the fluted cutting part and crossing into a center area of the basebody. It additionally comprises widened areas on both sides of thecenter area, giving its cross-section an overall bone-like appearance.Its opposite end areas are spherical or rounded, so that, in particular,the radially outer course of the core structure runs concentrically tothe outer jacket.

In an especially expedient embodiment, the core structure is designed tobe suitable for conducting coolant and extends from a rearward end to afront end face of the base body. For this purpose, in particular, aconventional, standardized coolant connection is expediently formed atthe rearward end of the base body. This typically comprises a transversegroove into which a coolant is fed from the machine tool.

At the front end face, coolant optionally exits the base body or istransferred to an interface with a tool tip into which the coolant canthen be further fed.

Taken as a whole, the machining tool is designed in an expedientembodiment as a carrier tool having at least one cutting element thatcan be secured to the base body, in particular a tool tip or cuttingplates. The base body is preferably manufactured from a tool steel. Thecutting element, in contrast, is made of a harder material such as asolid carbide or also a ceramic, for example. It is secured to the basebody in particular as a reversibly detachable insert.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are explained below in greaterdetail based on the figures, some of which are simplified illustrations.

FIG. 1 shows a side view of a machining tool designed as a modularcarrier tool;

FIG. 2 shows a sectional view through the machining tool as shown inFIG. 1 along intersecting line A-A;

FIG. 3 shows a sectional view through the machining tool as shown inFIG. 1 along intersecting line C-C;

FIG. 4 shows a sectional view through the machining tool alongintersecting line B-B;

FIG. 5 shows a sectional view of a grid-like core structure;

FIG. 6 shows a sectional view of a bionic core structure in the area ofthe intersecting line A-A as shown in FIG. 1; and

FIG. 7 shows a sectional view of a bionic core structure in the area ofthe intersecting line B-B as shown in FIG. 1.

Parts having the same effect are given the same reference numbers in thefigures.

DETAILED DESCRIPTION OF THE INVENTION

The machining tool 2 illustrated in FIG. 1 is designed as a modulardrill tool. It has a tool tip 4 in the form of a cutting element made ofsolid carbide or ceramic, which is reversibly and removably attached tothe frontal end of a base body 6. In the present invention, a tool tipis generally understood to mean the frontal end area of the machiningtool 2, i.e. a front end face area of the machining tool. In theexemplary embodiment according to FIG. 1, this is formed by thereplaceable tool tip 4. In the case of a carrier tool having plate seatsfor attaching (indexable) inserts as a cutting element, the area of theplate seat is understood to mean the tool tip. In a non-modular,one-piece tool, a front end area having an axial length, for example, inthe range of a nominal diameter of the machining tool 2 is referred toas the tool tip. In the exemplary embodiment according to FIG. 1, thetool tip 4 is clamped as a reversibly replaceable insert between twoclamping or retaining webs 7 of the base body 6.

The machining tool 2, and thus also the base body 6, as well as the tooltip 4 each extend in an axial direction 10 along a center axis 8 from arearward end to a front end. At the same time, this center axis 8defines a rotational axis around which the machining tool rotates in arotational direction D during operation.

The base body 6 is in turn divided into a rear shaft part 12, with whichthe machining tool 2 is held clamped in a tensioning piece of a machinetool during operation. A cutting part 16 provided with chip flutes 14 isconnected to the shaft part 12 in the axial direction 10. In theexemplary embodiment, the chip flutes 14 extend in a helical pattern.The end-face tool tip 4 has major cutting edges 18, each of whichtypically transitions into a minor cutting edge 20 on thecircumferential side. These are continued in the cutting part 16.

A support bevel 24 adjoins the minor cutting edge 20 opposite to thedirection of rotation.

As is described below based on FIGS. 2 through 5, the base body 6 is amonolithic base body 6, which is formed not from a solid material, butrather—at least in axial sections has a non-solid core structure 26. AsFIG. 2 in particular illustrates, this core structure is designed as acircular structure in the shaft part 12, as seen in the cross-sectionalview. To do this, the core structure 26 in this shaft part 12 ispreferably designed to have a constant radius R₁. A support bevel 24adjoins the minor cutting edge 20 opposite the direction of rotation.This cylindrical core structure 26 is surrounded by an outer jacket 28,which, except for a flattening 30 introduced externally, is designed asan annular ring. This outer mantel 28 has a radius R₂. The radius R₁ ofthe core structure 26 is preferably approximately 50 to 90% of the outerradius R₂. The core structure 26 has a core cross-sectional area A1, andthe machining tool 2 has a total cross-sectional area A2. This area isdefined by the area enclosed by the outer jacket 28, including thesurface of the outer jacket 28.

At the rearward end of the shaft part 12, the same is optionally closedoff with an end face plate formed of a solid material, i.e. thenon-solid core structure 26 is formed only in the interior of the shaftpart 12 without being visible from the rearward end face. A coolanttransfer point is expediently formed and incorporated into this solidend face plate. In particular, a transverse groove having through-holesrunning to the core structure 26 is introduced.

In the exemplary embodiment, the core structure 26 is limited, in asimilar manner, also in the axial direction 10 in the end area of theshaft part 12 by a solid partition 32 through which at least one, or inthe exemplary example, two, cut-outs 34, penetrate. Alternatively, thecore structure 26 also spans uninterrupted from the shaft part 12 intothe cutting part 6 and without partition 32. A partition 32 is providedparticularly in machining tools 2 without internal coolant supply.However, coolant supply is made possible in principle via the cut-outs34 in the cutting part 16.

In the front area of the machining tool 2, i.e. in the area of the tooltip 4, at least one outlet point 35 for coolant or lubricant isprovided. Multiple outlet points 35, which are oriented for exampletoward cutting areas, are preferably formed in a front end face or arealso formed circumferentially. The outlet point 35 can be designed as aborehole in a conventional manner. However, it is likewise preferablycreated by means of the 3D printing method and is geometrically complex.The core structure 26 is preferably directed to the outside to form theoutlet point 35. In the exemplary embodiment illustrated in FIG. 1, anoutlet point 35 is formed for example in a circumferential wall 36 inthe area of the tool tip and is formed in particular as a porousstructure. The outlet point 35 in the exemplary embodiment is thusgenerally integrated into the retaining webs 7.

The core structure 26 continues into the cutting part 16 itself (FIG.4). Due to the chip flutes 14 and to the circumferential geometry of thebase body 6 modified thereby, the cross-sectional geometry of the corestructure 26 is adapted in particular such that it is enveloped entirelyby roughly the same wall thickness as that of the outer jacket 28. Inparticular, the core structure 26 is designed to be elongated in thecutting part 16 and has a center area 37, which transitions into widenedareas 38 at both ends. The outer edge of each said widened area has anaccurate contour, so that they run concentrically to the circumferentialline of the base body 6.

The core structure 26 is preferably homogeneous even over its entirecross sectional area A1. Alternatively, additional supports can beprovided in a manner not further illustrated here. Separate coolantchannels are expediently not formed in the embodiment variants of FIG.1.

According to a first embodiment variant, the core structure 26 isdesigned as a porous structure. According to a second embodiment variantillustrated in FIG. 5, in contrast, the core structure 26 is designed asa grid-like structure, in particular as a honeycomb-shaped structure.This structure has a plurality of individual channels 40 extending inthe axial direction 10. Rectangular channels are schematicallyillustrated in FIG. 5. The individual channels 40 are each separatedfrom one another by partitions 42. These partitions 42 preferably haveonly a slight material thickness of, for example, below 0.3 mm and,particularly, below 0.15 mm. The individual channels 40 usually have achannel width W of below 0.5 mm.

Further alternatives for the core structure 26 are illustrated in FIG. 6and FIG. 7. In these embodiment variants, the core structure 26 isdesigned to be what is referred to as a bionic structure, in which—incontrast to the grid-like structure illustrated in FIG. 5—the individualpartitions 42 are unordered and do not follow a pattern, at least not arecurring pattern.

It is possible in principle for the different structures to be combinedwith one another and, for example, to be formed next to one anotherwithin a sectional plane. Alternatively, the structure varies in theaxial direction 10. The specific manufacturing method allows nearly alldesired combinations and variations. In particular, differentstructures, particularly of different porosity, are present in thecutting part 16 and the shaft part 12. Thus, for example, the cuttingpart 16 is of greater porosity than the shaft part 12, or vice versa.

The base body 6 is manufactured using what is referred to as a 3Dprinting method. In this method, a metal powder is worked successivelyand thus layer-by-layer by means of laser treatment according to thedesired cross-sectional geometry of each layer and melted or sintered toform a cohesive, monolithic sub-body. In this process, eachcross-sectional contour of each layer is predefined by the laser. Withthis 3D printing method, nearly any arbitrary and complex and, inparticular, variable cross-sectional geometries can be created. Inparticular, the core structure 26 described by FIGS. 2 through 5 andhaving the solid enveloping outer mantel 28 is formed using this method.The entire base body 6 is thus formed as a one-piece, monolithic body byutilizing this manufacturing method. This body can also undergofinishing work, if necessary, following the 3D printing process.

The base body 6 is preferably made of tool steel according to DIN EN10027, for example with a material number 1.2709 and/or 1.2344.

1. A machining tool comprising a monolithic base body extending in anaxial direction wherein the base body, in at least one section, has anon-solid core structure which is encased in a solid outer jacket. 2.The machining tool as claimed in claim 1, wherein the core structure isporous, grid-like, bionic or a combination thereof.
 3. The machiningtool as claimed in claim 1, wherein the core structure is ahoneycomb-like structure.
 4. The machining tool as claimed in claim 1,wherein, if the core structure is porous, the core structure has aporosity ranging between 5.2% and 90% and, wherein, if the corestructureis grid-like, the core structure has a plurality of canalsextending in a longitudinal direction and having a canal width (W) lessthan 0.5 mm.
 5. The machining tool as claimed in claim 1, wherein thecore structure has a circular cross-section.
 6. The machining tool asclaimed in claim 1, wherein the core structure covers 5% to 80% of anentire cross-sectional area (A2) of the base body.
 7. The machining toolas claimed in claim 1, wherein the core structure has differentcross-sectional areas (A1) in the axial direction.
 8. The machining toolas claimed in claim 1, wherein the base body has a shaft part, as wellas a front cutting part, each with a core structure, and wherein thecore structure extends into the cutting part from the shaft part.
 9. Themachining tool as claimed in claim 1, further comprising a flutedcutting part, and wherein the core structure, in an area of the cuttingpart, extends transversely over a center area and has widened areas onboth sides of the center area.
 10. The machining tool as claimed inclaim 1, wherein the core structure is designed to conduct coolant. 11.The machining tool as claimed claim 1, wherein the machining tool isdesigned as a carrier tool having a cutting element that is adapted tobe secured onto the base body, and wherein the base body is manufacturedfrom tool steel.
 12. A method for manufacturing a rotating tool having amonolithic base body extending in an axial direction, wherein the basebody is manufactured by a 3D printing method.